Industry spends significant resources in the processing of a variety of commercially important substrate surfaces. Commercial substrates that can require surface processing include, to name a few, materials involved in the manufacture of microelectronic devices such as integrated semiconductor circuits (e.g., semiconductor wafers), display screens comprising liquid crystals, electric circuits on boards of synthetic material (circuit boards), and other commercially significant materials and products. These devices can be fabricated according to a series of processing steps, including one or a number of steps for processing a device surface. Methods for processing these and other substrate surfaces can include steps of cleaning, etching, rinsing, drying, or otherwise processing surfaces of substrates for further processing and use.
Many such processing methods, and a variety of commercial processing equipment, are known for substrate processing. According to their use, substrate surfaces are treated with one or more liquid processing materials followed by rinsing and drying.
With respect to the processing of microelectronic devices, these can require one or more of cleaning, etching, rinsing, and drying, in a contaminant-free environment. Various types of available processing equipment are capable of exposing one or a number of wafer surfaces to different processing fluids (e.g., liquids and/or gase), to accomplish one and preferably a series of surface processing operations. These machines can perform a series of various cleaning and etching steps, followed by rinsing and drying, to a highly contaminant-free surface.
Processing generally includes a series of discrete steps such as a cleaning step followed by a wet etching step. Both of these steps involve application of a suitable treatment chemical to the substrate surface, e.g., a gaseous or liquid cleaning solution or an etching or oxidizing agent. The cleaning, etching, or oxidizing agent must subsequently be removed. This is often accomplished by a separate “rinsing” step, which uses a rinsing fluid such as water to dilute and ultimately wash away the previously-applied materials. Different types of machines accomplish the rinse step in different fashions. Some rinse by immersion of the wafer. Some rinse by spraying fluids onto wafer surfaces. Some machines include the ability to heat wafers or expose wafers to inert environments, some rinse by flowing a liquid past a wafer, and some include the ability to remove liquids with centrifugal force by spinning or rotating the wafers on a turntable or carousel, either about their own axis or about a common axis. Some use combos of these.
After rinsing, the rinsing fluid is desirably removed with a drying step. The rinsing and drying steps are in general, separate processing events. Drying should typically not begin until the substrate surface has been rinsed as completely as possible of contaminants and processing chemicals.
Drying processes can include one or more of the use of heat, dry gases such as nitrogen, centrifugal force, and even the use of certain polar organic compounds such as isopropyl alcohol, 1-methoxy-2-propanol, di-acetone alcohol, and ethylglycol. See e.g., U.S. Pat. Nos. 5,571,337 (Mohindra et al.) and 5,271,774 (Leenaars et al.).
For processing microelectronic devices, certain surface properties are desired. With microelectronic devices and silicon-containing materials in particular, etching the surface is intended to remove surface oxides. It is desirable that the processed surface, after being etched, rinsed, dried, or otherwise processed, exhibits a low amount of surface oxides. Thus, after removing oxides in the etching step, processes are preferred which avoid re-oxidation of the surface during subsequent processing, including rinsing and drying. Instead of forming surface oxides during these steps, it would be desirable for rinsing and drying steps to promote “passivation” of surface silica with hydrogen atoms. Testing a surface by measuring the contact angle between a drop of water and the surface can provide an indication of how well oxides have been removed.
Other desirable properties include minimization of surface particles, electrostatic charge, and water spots.
There exists a continuing need to improve available methods and equipment relating to processing commercial substrates such as microelectronic devices. It is a continuing goal to process substrate surfaces to desired surface properties, e.g., minimal surface particles, electrostatic charge, and water spots. With respect to microelectronic devices, it may also desirable to process substrate surfaces to have desired minimal concentrations of surface oxides; surface composition can be measured by ESCA (Electron Spectrum for Chemical Analysis).